Imaging device having autofocus capability

ABSTRACT

Herein disclosed is an imaging device having an imaging optical system, the device including: an imaging element configured to include a plurality of first pixels and a plurality of second pixels arranged along a predetermined direction; a first processor configured to execute focal detection processing by a phase difference detection system based on charge signals obtained from the plurality of second pixels; and a second processor configured to execute specific processing based on charge signals obtained from the plurality of first pixels, the specific processing being different from the focal detection processing by a phase difference detection system and being necessary for a function of the imaging device.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 14/847,400, filed Sep. 8, 2015, which is acontinuation application of U.S. patent application Ser. No. 14/244,598,filed Apr. 3, 2014, (now U.S. Pat. No. 9,143,675, which is acontinuation application of U.S. patent application Ser. No. 11/983,962,filed Nov. 13, 2007, which claims priority from Japanese PatentApplication JP 2006-319783 filed in the Japan Patent Office on Nov. 28,2006, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an imaging device having an imagingoptical system.

2. Description of the Related Art

As a technique in a digital camera (imaging device), a technique isknown in which auto focus control by a phase difference detection system(hereinafter, referred to also as “phase difference AF”) is implementedby using an imaging element that includes pixels each having dividedinside and plural photoelectric converters (hereinafter, referred toalso as “divided pixels”).

For example, according to the technique disclosed in Japanese PatentLaid-open No. 2001-305415 (hereinafter, Patent Document 1), therespective photoelectric converters in pixels each divided into twoareas receive light beams that have passed through different areas ofthe pupil of an imaging lens (imaging optical system) to thereby createa pair of image sequences, and the shift amount regarding this pair ofimage sequences is obtained, which allows the phase difference AF withuse of an imaging element. Furthermore, Patent Document 1 discloses alsoa feature that AF control by a contrast detection system (hereinafter,referred to also as “contrast AF”) is implemented by using outputs fromthe photoelectric converters in these divided pixels.

However, in the technique of Patent Document 1, the contrast AF isperformed by using the divided pixels provided for the phase differenceAF (pixels for phase difference AF). Therefore, there is a fear that thefocusing accuracy of this contrast AF is lower than that of existingcontrast AF. Specifically, in existing contrast AF, charge signals ofnon-divided pixels, of which inside is not divided, are utilized. Incontrast, the respective photoelectric converters in divided pixels forreceiving light beams that have passed through a part of the lens pupilhave sensitivity lower than that of existing non-divided pixels.Accordingly, it is difficult for the contrast AF by use of the outputsof the divided pixels to ensure accuracy equal to that of existingcontrast AF.

In addition, if auto exposure control (AE), auto white balance control(AWB), and so on are implemented based on the outputs of the dividedpixels similarly to the above-described contrast AF, there is a fearthat the accuracy of these specific controls necessary for camerafunctions is also lower than that of existing controls.

SUMMARY OF THE INVENTION

There is a need for the present invention to provide an imaging devicethat can execute specific processing necessary for camera functionsother than phase difference AF with high accuracy by using an imagingelement that has pixels for the phase difference AF.

According to an embodiment of the present invention, there is providedan imaging device having an imaging optical system. The device includes(a) an imaging element configured to include a plurality of first pixelsand a plurality of second pixels arranged along a predetermineddirection, (b) a first processor configured to execute focal detectionprocessing by a phase difference detection system based on chargesignals obtained from the plurality of second pixels, and (c) a secondprocessor configured to execute specific processing based on chargesignals obtained from the plurality of first pixels. The specificprocessing is different from the focal detection processing by a phasedifference detection system and is necessary for a function of theimaging device. The plurality of first pixels receive a subject lightbeam that has passed through the entire area of the exit pupil of theimaging optical system, and the plurality of second pixels receivesubject light beams that have passed through a pair of partial areas ofthe exit pupil. The first processor creates a pair of image sequencesbased on charge signals from the second pixels that receive subjectlight beams that have passed through the pair of partial areas, anddetects the amount of shift along the predetermined direction regardingthe pair of image sequences, to thereby execute the focal detectionprocessing by a phase difference detection system.

According to the embodiment of the present invention, focal detectionprocessing by a phase difference detection system is executed based oncharge signals obtained from the plurality of second pixels that receivesubject light beams that have passed through a pair of partial areas ofthe exit pupil of the imaging optical system. Furthermore, based oncharge signals obtained from the plurality of first pixels that receivea subject light beam that has passed through the entire area of the exitpupil of the imaging optical system, specific processing that isdifferent from the focal detection processing by a phase differencedetection system and is necessary for a function of the imaging deviceis executed. As a result, by using an imaging element having pixels (theabove-described second pixels) for phase difference AF, specificprocessing necessary for camera functions other than the phasedifference AF can be executed with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the appearance configuration of an imagingdevice 1 according to an embodiment of the present invention;

FIG. 2 is a diagram showing the appearance configuration of the imagingdevice 1;

FIG. 3 is a vertical sectional view of the imaging device 1;

FIG. 4 is a block diagram showing the electric configuration of thewhole of the imaging device 1;

FIG. 5 is a diagram for explaining the configuration of an imagingelement 101;

FIG. 6 is a diagram for explaining the configuration of a G pixel 11 grhaving divided inside;

FIG. 7 is a diagram for explaining the principle of phase difference AFemploying the imaging element 101;

FIG. 8 is a diagram showing a simulation result when the focal plane isdefocused to the 200-μm-closer side from the imaging plane of theimaging element 101;

FIG. 9 is a diagram showing a simulation result when the focal plane isdefocused to the 100-μm-closer side from the imaging plane;

FIG. 10 is a diagram showing a simulation result of the focused state inwhich the focal plane corresponds with the imaging plane;

FIG. 11 is a diagram showing a simulation result when the focal plane isdefocused to the 100-μm-remoter side from the imaging plane;

FIG. 12 is a diagram showing a simulation result when the focal plane isdefocused to the 200-μm-remoter side from the imaging plane;

FIG. 13 is a diagram for explaining a graph Gc that indicates therelationship between the defocus amount and the centroid positiondifference between a pair of image sequences;

FIG. 14 is a diagram for explaining the principle of contrast AF;

FIG. 15 is a flowchart showing the basic operation of the imaging device1;

FIG. 16 is a diagram for explaining the AF operation of the imagingdevice 1;

FIG. 17 is a diagram for explaining the configuration of an imagingelement 101A according to a modification example of the presentinvention; and

FIG. 18 is a diagram for explaining the configuration of an imagingelement 101B according to another modification example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

<Appearance Configuration of Imaging Device>

FIGS. 1 and 2 are diagrams showing the appearance configuration of animaging device 1 according to an embodiment of the present invention.FIGS. 1 and 2 are front view and rear view, respectively. FIG. 3 is avertical sectional view of the imaging device 1.

The imaging device 1 is configured as e.g. a single-lens reflex digitalstill camera, and includes a camera body 10 and an imaging lens 2 as aninterchangeable lens that can be freely detached from the camera body10.

Referring to FIG. 1, the following parts are provided on the front faceside of the camera body 10: a mount part 301 that is disposed atsubstantially the center of the camera front face and on which theimaging lens 2 is mounted; a lens interchange button 302 disposed at theright of the mount part 301; a grip part 303 that is provided in aprotruding manner at the left end of the camera front face (left sidewith respect to the X direction) and allows a user to surely grasp thecamera with one hand (or both hands); a mode setting dial 305 disposedat upper left part of the camera front face (upper left side withrespect to the Y direction); a control value setting dial 306 disposedat upper right part of the camera front face; and a shutter button 307disposed on the top face of the grip part 303.

Referring to FIG. 2, the following parts are provided on the rear faceside of the camera body 10: a liquid crystal display (LCD) 311; asetting button group 312 disposed at the left of the LCD 311; an arrowkey 314 disposed at the right of the LCD 311; and a push button 315disposed at the center of the arrow key 314. Furthermore, the followingparts are also provided on the rear face side of the camera body 10: anelectronic view finder (EVF) 316 disposed above the LCD 311; an eyecup321 surrounding the EVF 316; a main switch 317 disposed at the left ofthe EVF 316; an exposure correction button 323 and an AE lock button 324that are disposed at the right of the EVF 316; and a flash part 318 anda connection terminal 319 that are provided above the EVF 316.

On the mount part 301, plural electric contacts for electric connectionto the mounted imaging lens 2, couplers for mechanical connection, andso on are provided.

The lens interchange button 302 is pushed down at the time of removal ofthe imaging lens 2 mounted on the mount part 301.

The grip part 303 is to allow a user to grasp the imaging device 1 atthe time of imaging, and is provided with surface undulation in matchingwith the finger shape for higher fitting property. Inside the grip part303, a cell holder and card holder (not shown) are provided. In the cellholder, a cell 69B (see FIG. 4) is housed as a camera power source. Inthe card holder, a recording medium (e.g., memory card) for recordingthe image data of captured images is detachably housed. The grip part303 may be provided with a grip sensor for detecting whether or not thegrip part 303 is grasped by a user.

The mode setting dial 305 and the control value setting dial 306 areformed of a member that has a substantially circular disk shape and canrotate in a plane substantially parallel to the top face of the camerabody 10. The mode setting dial 305 is to select one of modes andfunctions incorporated in the imaging device 1, such as an auto exposure(AE) control mode, an auto focus (AF) control mode, various imagingmodes typified by a still image mode for capturing one still image and acontinuous imaging mode for performing continuous imaging, and areproduction mode for reproducing recorded images. The control valuesetting dial 306 is to set control values for the various functionsincorporated in the imaging device 1.

The shutter button 307 is a push-down switch that can be halfway pusheddown so as to be in the “halfway-pushed state” and can be further pusheddown so as to be in the “fully-pushed state”. When the shutter button307 is halfway pushed (S1) in a still image mode, preparation operationfor capturing a still image of a subject (preparation operation such assetting of the exposure control value and focus adjustment) is executed.When the shutter button 307 is fully pushed (S2), imaging operation (aseries of operation including exposure of an imaging sensor,predetermined image processing for an image signal obtained through theexposure, and recording in a memory card or the like) is executed.

The LCD 311 includes a color liquid crystal panel that can displayimages. The LCD 311 is to display an image captured by an imagingelement 101 (FIG. 3) and a reproduced image that has been recorded, andis to display a setting screen for the functions and modes incorporatedin the imaging device 1. Instead of the LCD 311, an organic EL displayor plasma display may be used.

The setting button group 312 includes buttons that allow operation forthe various functions incorporated in the imaging device 1.Specifically, the setting button group 312 includes e.g. a selectionsettlement switch for settling the details selected on a menu screendisplayed on the LCD 311, selection cancel switch, menu displayingswitch for a change of the contents of the menu screen, displayingON/OFF switch, and displaying enlargement switch.

The arrow key 314 is formed of an annular member that has pluralpush-down parts (triangle-mark parts in the drawing) disposed along thecircumferential direction with a constant interval, and is so configuredthat pressing operation for the push-down parts is detected throughcontacts (switches, not shown) provided corresponding to the respectivepush-down parts. The push button 315 is disposed at the center of thearrow key 314. The arrow key 314 and the push button 315 are used toinput instructions regarding a change of the imaging magnification(movement of the zoom lens in the wide direction and tele direction),frame stepping of a recorded image to be reproduced on the LCD 311 orthe like, setting of imaging conditions (diaphragm value, shutter speed,the presence or absence of flash lighting, etc.), and so on.

The EVF 316 includes e.g. a color liquid crystal panel that can displayimages, and is to display an image captured by the imaging element 101(FIG. 3) and a reproduced image that has been recorded. On the EVF 316and the LCD 311, live-view (preview) displaying is performed in which asubject is displayed in a moving image manner based on image signalssequentially created by the imaging element 101 before actual imaging(imaging for image recording). This permits a user to visually recognizethe subject to be actually imaged by the imaging element 101.

The main switch 317 is formed of a dual-contact slide switch thatlaterally slides. When the main switch 317 is set to the left, the powersupply of the imaging device 1 is turned on. When the main switch 317 isset to the right, the power supply is turned off.

The flash part 318 is configured as a pop-up built-in flash. When anexternal flash or the like is attached to the camera body 10, theconnection terminal 319 is used for the connection.

The eyecup 321 is a U-character shaped light-shielding member thatsuppresses the entry of external light into the EVF 316.

The exposure correction button 323 is to manually adjust the exposurevalue (diaphragm value and shutter speed), and the AE lock button 324 isto fix exposure.

The imaging lens 2 functions as a lens window that captures light(optical image) from a subject, and functions also as an imaging opticalsystem for guiding the subject light to the imaging element 101 disposedinside the camera body 10. By pushing down the above-described lensinterchange button 302, the imaging lens 2 can be removed from thecamera body 10.

The imaging lens 2 includes a lens group 21 composed of plural lensesthat are serially arranged along an optical axis LT (FIG. 3). This lensgroup 21 includes a focus lens 211 (see FIG. 4) for adjustment of thefocal point and a zoom lens 212 (see FIG. 4) for magnification changes.These lenses are driven in the direction of the optical axis LT, so thatthe magnification change and focal adjustment are performed.Furthermore, at a proper position on the outer circumference of the lensbarrel of the imaging lens 2, an operating ring that can rotate alongthe outer circumferential plane of the lens barrel is provided. Inresponse to manual or auto operation, the zoom lens 212 moves in theoptical axis direction depending on the rotation direction and rotationamount of the operating ring, so that the zoom magnification (imagingmagnification) is set to the value corresponding to the position of thelens movement destination.

The imaging element 101 is disposed on the optical axis LT of the lensgroup 21 included in the imaging lens 2 mounted on the camera body 10 insuch a manner as to be perpendicular to the optical axis LT. As theimaging element 101, a Bayer-arrangement CMOS color area sensor (CMOSimaging element) is used, in which plural pixels each having e.g. aphotodiode are two-dimensionally arranged in a matrix and e.g. red (R),green (G), and blue (B) color filters having different spectroscopiccharacteristics are provided at the ratio of 1:2:1 on thelight-receiving planes of the respective pixels. The imaging element(imaging sensor) 101 converts an optical image of a subject formedthrough the lens group 21 into analog electric signals (image signals)of the respective color components of R, G, and B, and outputs thesignals as R, G, and B image signals. The configuration of this imagingelement 101 will be described in detail later.

In front of the imaging element 101, a shutter unit 40 is disposed. Thisshutter unit 40 has a film body that vertically moves, and is configuredas a mechanical focal plane shutter that carries out operations ofopening and blocking the optical path of subject light guided to theimaging element 101 along the optical axis LT. The shutter unit 40 canbe omitted if the imaging element 101 can be fully electronicallyshuttered.

<Electric Configuration of Imaging Device 1>

FIG. 4 is a block diagram showing the electric configuration of thewhole of the imaging device 1. The same members and so on in FIG. 4 asthose in FIGS. 1 to 3 are given the same numerals. For convenience ofdescription, initially the electric configuration of the imaging lens 2will be described below.

In addition to the lens group 21 serving as the above-described imagingoptical system, the imaging lens 2 includes a lens drive mechanism 24, alens position detector 25, a lens controller 26, and a diaphragm drivemechanism 27.

For the lens group 21, the focus lens 211, the zoom lens 212, and adiaphragm 23 for adjusting the amount of light incident on the imagingelement 101 provided in the camera body 10 are held in the lens barrelalong the direction of the optical axis LT (FIG. 3). This allowscapturing of an optical image of a subject and formation of the opticalimage on the imaging element 101. The focal adjustment operation iscarried out through driving of the lens group 21 in the direction of theoptical axis LT by an AF actuator 71M in the camera body 10.

The lens drive mechanism 24 is formed of e.g. a helicoid and a gear (notshown) for rotating the helicoid. The lens drive mechanism 24 receivesdriving force from the AF actuator 71M via a coupler 74 to thereby movethe focus lens 211 and so on in the direction parallel to the opticalaxis LT. The movement direction and movement amount of the focus lens211 conform to the rotation direction and the number of rotations,respectively, of the AF actuator 71M.

The lens position detector 25 includes an encode plate on which pluralcode patterns are formed along the direction of the optical axis LT witha predetermined pitch within the movement range of the lens group 21,and an encoder brush that moves integrally with the lens barrel 22 insuch a manner as to be in sliding contact with the encode plate. Thelens position detector 25 detects the movement amount of the lens group21 at the time of focal adjustment. The lens position detected by thelens position detector 25 is output as e.g. the number of pulses.

The lens controller 26 is formed of e.g. a microcomputer that includes aROM storing therein a control program and a memory 261 formed of a flashmemory or the like storing therein data relating to status information.Furthermore, the lens controller 26 includes a communication unit 262that communicates with a main controller 62 in the camera body 10. Thiscommunication unit 262 transmits to the main controller 62 e.g. statusinformation data such as the focal length, exit pupil position,diaphragm value, focus distance, and peripheral light amount status ofthe lens group 21. On the other hand, the communication unit 262receives e.g. the drive amount of the focus lens 211 from the maincontroller 62. Furthermore, at the time of imaging, data such as focallength information and diaphragm value obtained after the completion ofAF operation are transmitted from the communication unit 262 to the maincontroller 62. In the memory 261, the above-described status informationdata of the lens group 21, data of e.g. the drive amount of the focuslens 211 transmitted from the main controller 62, and so on are stored.

The diaphragm drive mechanism 27 receives driving force from a diaphragmdrive actuator 73M via a coupler 75 to thereby change the diaphragmdiameter of the diaphragm 23.

The electric configuration of the camera body 10 will be describedbelow. In addition to the above-described imaging element 101, shutterunit 40, and so on, the camera body 10 includes an analog front-end(AFE) 5, an image processor 61, an image memory 614, the main controller62, a flash circuit 63, an operating unit 64, VRAMs 65 (65 a and 65 b),a card I/F 66, a memory card 67, a communication I/F 68, a power supplycircuit 69, the cell 69B, a focus drive controller 71A, the AF actuator71M, a shutter drive controller 72A, a shutter drive actuator 72M, adiaphragm drive controller 73A, and the diaphragm drive actuator 73M.

The imaging element 101 is formed of a CMOS color area sensor asdescribed above. A timing control circuit 51 to be described latercontrols imaging operation such as the start (and end) of exposureoperation of the imaging element 101, selection of the outputs of therespective pixels included in the imaging element 101, and reading-outof pixel signals.

The AFE 5 supplies the imaging element 101 with a timing pulse forcausing the imaging element 101 to carry out predetermined operation.Furthermore, the AFE 5 executes predetermined signal processing for animage signal (group of analog signals received by the respective pixelsof the CMOS area sensor) output from the imaging element 101, to therebyconvert the signal into a digital signal and output it to the imageprocessor 61. This AFE 5 includes the timing control circuit 51, asignal processor 52, and an A/D converter 53.

The timing control circuit 51 produces predetermined timing pulses(vertical scan pulse φVn, horizontal scan pulse φVm, and pulses forgenerating a reset signal φVr and so on) based on a reference clockoutput from the main controller 62, and outputs the timing pulses to theimaging element 101 for control of the imaging operation of the imagingelement 101. In addition, the timing control circuit 51 outputspredetermined timing pulses to the signal processor 52 and the A/Dconverter 53 to thereby control the operation of the signal processor 52and the A/D converter 53.

The signal processor 52 executes predetermined analog signal processingfor an analog image signal output from the imaging element 101. Thissignal processor 52 includes a correlated double sampling (CDS) circuit,an auto gain control (AGC) circuit for amplifying a charge signal outputfrom the imaging element 101, a clamp circuit, and so on.

In the AGC circuit of the signal processor 52, charge signals fromdivided G pixels 11 gr to be described later are amplified with a gain(amplification factor) α, and charge signals from non-divided pixels (Gpixels 11 gb, R pixels 11 r, and B pixels 11 b) to be described laterare amplified with a gain β different from the gain α. The reason forthis amplification with different gains is that the sensitivity of thedivided G pixels, which receive light beams that have passed through apart of the exit pupil of the imaging lens 2, is lower than that of thenon-divided pixels, and thus there is a need to amplify signals from thedivided G pixels with a gain higher than that for the non-divided pixelsto thereby ensure a proper output level.

The A/D converter 53 converts analog R, G, and B image signals outputfrom the signal processor 52 into a digital image signal composed ofplural bits (e.g., 12 bits) based on the timing pulse output from thetiming control circuit 51.

The image processor 61 executes predetermined signal processing forimage data output from the AFE 5 to thereby create an image file, andincludes a black level correction circuit 611, a white balance controlcircuit 612, and a gamma correction circuit 613. Image data loaded inthe image processor 61 is written to the image memory 614 insynchronization with reading from the imaging element 101, and from thenon the image processor 61 accesses this image data written to the imagememory 614 for processing in the respective blocks in the imageprocessor 61.

The black level correction circuit 611 corrects the black level of theR, G, and B digital image signals arising from the A/D conversion by theA/D converter 53 to a reference black level.

The white balance correction circuit 612 carries out level conversion(white balance (WB) adjustment) for the digital signals of therespective color components of R, G, and B based on the reference whitedependent upon the light source. Specifically, based on WB adjustmentdata given from the main controller 62, the white balance correctioncircuit 612 specifies from an imaging subject a part that is estimatedto be originally white based on luminance, chroma, and other data.Furthermore, the white balance correction circuit 612 calculates,regarding the specified part, the average of the R, G, and B colorcomponents, the G/R ratio, and the G/B ratio, and carries out levelcorrection by using the calculated parameters as the correction gainsfor R and B.

The gamma correction circuit 613 corrects the grayscale characteristicof the image data of which WB is adjusted. Specifically, the gammacorrection circuit 613 carries out nonlinear transform and offsetadjustment by using a gamma correction table in which the level of imagedata is set in advance for each color component.

At the time of the imaging mode, the image memory 614 temporarily storestherein image data output from the image processor 61, and is used as awork area for predetermined processing by the main controller 62 forthis image data. Furthermore, at the time of the reproduction mode,image data read out from the memory card 67 is temporarily stored in theimage memory 614.

The main controller 62 is formed of e.g. a microcomputer that includes aROM storing therein a control program and a memory such as a flashmemory temporarily storing therein data. The main controller 62 controlsthe operation of the respective units in the imaging device 1.

Furthermore, for the imaging element 101, the main controller 62controls pixel reading of two kinds of modes (live-view read mode and AFread mode).

In the live-view read mode of the imaging element 101, the cycle (framerate) of the pixel reading is set to 60 fps. Furthermore,decimation-reading of pixels is carried out for the imaging element 101,so that e.g. an image of 640×480 pixels in the VGA size is created as animage for live-view displaying. In this decimation-reading, thenon-divided pixels to be described later (the non-divided G pixels 11gb, the R pixels 11 r, and the B pixels 11 b) are read out. The imagescreated through the decimation-reading from the imaging element 101 aresequentially displayed on the EVF 316 (or the LCD 311), so thatlive-view displaying of a subject is performed.

In the AF read mode of the imaging element 101, auto focus control iscarried out in such a way that the cycle (frame rate) of the pixelreading is set to 240 fps and the divided G pixels 11 gr and thenon-divided G pixels 11 gb to be described later are read out. Also inthe AF read mode, live-view displaying is performed by reading out at 60fps the non-divided G pixels 11 gb, the R pixels 11 r, and the B pixels11 b from the imaging element 101.

The flash circuit 63 regulates, in the flash imaging mode, the lightemission amount of the flash part 318 or an external flash connected tothe connection terminal 319 to the light emission amount designed by themain controller 62.

The operating unit 64 includes the above-described mode setting dial305, control value setting dial 306, shutter button 307, setting buttongroup 312, arrow key 314, push button 315, main switch 317, and so on.The operating unit 64 is used to input operation information to the maincontroller 62.

The VRAMs 65 a and 65 b have memory capacity for image signalscorresponding to the numbers of pixels of the LCD 311 and the EVF 316,and serve as buffer memories between the main controller 62 and the LCD311 and the EVF 316. The card I/F 66 is an interface for permittingsignal transmission/reception between the memory card 67 and the maincontroller 62. The memory card 67 is a recording medium in which imagedata created by the main controller 62 is stored. The communication I/F68 is an interface for allowing image data and so on to be transmittedto a personal computer and other external apparatuses.

The power supply circuit 69 is formed of e.g. a constant voltagecircuit, and produces voltage (e.g., 5 V) for driving the entire imagingdevice 1, including control units such as the main controller 62, theimaging element 101, and other various drive units. The energization ofthe imaging element 101 is controlled based on a control signal suppliedfrom the main controller 62 to the power supply circuit 69. The cell 69Bis a primary cell such as an alkaline dry cell or a secondary cell suchas a nickel hydride rechargeable battery, and serves as a power sourcefor supplying the entire imaging device 1 with power.

The focus drive controller 71A creates, based on an AF control signalgiven from the main controller 62, a drive control signal for the AFactuator 71M necessary to move the focus lens 211 to the focus position.The AF actuator 71M is formed of a stepping motor or the like, and giveslens driving force to the lens drive mechanism 24 of the imaging lens 2via the coupler 74.

The shutter drive controller 72A creates a drive control signal for theshutter drive actuator 72M based on a control signal given from the maincontroller 62. The shutter drive actuator 72M drives the shutter unit 40so that the shutter unit 40 can be opened and closed.

The diaphragm drive controller 73A creates a drive control signal forthe diaphragm drive actuator 73M based on a control signal given fromthe main controller 62. The diaphragm drive actuator 73M gives drivingforce to the diaphragm drive mechanism 27 via the coupler 75.

The camera body 10 further includes a phase difference AF arithmeticcircuit 76 and a contrast AF arithmetic circuit 77 that performarithmetic operation necessary at the time of auto focus (AF) based onimage data of which black level has been corrected, output from theblack level correction circuit 611.

A detailed description will be made below about AF operation of theimaging device 1 by use of the phase difference AF arithmetic circuit 76and the contrast AF arithmetic circuit 77.

<AF Operation of Imaging Device 1>

The imaging device 1 is configured to allow AF by a phase differencedetection system (phase difference AF), in which the imaging element 101receives light that has been transmitted (has passed) through differentparts of the exit pupil to thereby detect the focal point. Theconfiguration of this imaging element 101 and the principle of the phasedifference AF employing the imaging element 101 will be described below.

FIG. 5 is a diagram for explaining the configuration of the imagingelement 101.

The imaging element 101 has red (R) pixels 11 r, green (G) pixels 11 g,and blue (B) pixels 11 b in which color filters of R, G, and B,respectively, are provided on photodiodes. For each of the pixels 11 (11r, 11 g, 11 b), one microlens ML is provided. For convenience ofillustration, adjacent microlenses ML overlap with each other in FIG. 5.However, in a practical imaging element, the microlenses ML are arrangedwithout overlapping.

The G pixels 11 g include plural G pixels 11 gr arranged along thedirection of Gr lines L1 (horizontal direction) and plural G pixels 11gb arranged along Gb lines L2. In each of the G pixels 11 gr on the Grlines L1, the pixel inside is divided into eight areas along thedirection of the Gr lines L1. Specifically, as shown in FIG. 6, in the Gpixel 11 gr, eight photoelectric converters 111 to 118 are arrangedalong the direction of the Gr line L1. Each of the photoelectricconverters 111 to 118 has an independent photodiode, which permitsreading out of accumulated charges through photoelectric conversion. Inthe charge reading from the imaging element 101, the charge reading fromthe G pixels 11 gr, of which inside is divided, and that from the othernon-divided pixels (the G pixels 11 gb, the R pixels 11 r, and the Bpixels 11 b) can be simultaneously carried out in such a way that thereading method for the G pixels 11 gr is made different from that forthe other non-divided pixels. Hereinafter, the G pixel 11 gr, of whichinside is divided, will be referred to as “divided G pixel” (referred toalso as “divided pixel” simply). On the other hand, the G pixel 11 gb,of which inside is not divided, will be referred to as “non-divided Gpixel” (referred to also as “non-divided pixel” simply).

The principle of the phase difference AF by use of the imaging element101 having the above-described divided G pixels 11 gr will be describedin detail below.

FIG. 7 is a diagram for explaining the principle of the phase differenceAF employing the imaging element 101.

The description of the principle is based on the following assumption.Specifically, when the actual diaphragm of the imaging lens (imagingoptical system) 2 is equivalent to e.g. F5.6, in the divided G pixel 11gr, a light beam Ta that has passed through a right-side part of an exitpupil Ep passes through a green color filter 12 and forms an image onthe photoelectric converter 113, which is the third converter from theleft end of the divided G pixel 11 gr. On the other hand, a light beamTb that has passed through a left-side part of the exit pupil Ep passesthrough the green color filter 12 and forms an image on thephotoelectric converter 116, which is the fifth converter from the leftend (third converter from the right end) of the divided G pixel 11 gr.That is, in contrast to the plural non-divided pixels including thenon-divided G pixels 11 gb, the R pixels 11 r, and the B pixels 11 b,which receive a subject light beam that has passed through the entirearea of the exit pupil Ep of the imaging lens 2, the plural divided Gpixels 11 gr receive the subject light beams Ta and Tb that have passedthrough a pair of partial areas of the exit pupil Ep of the imaging lens2. Hereinafter, light-reception data obtained from the photoelectricconverter 113 will be referred to as “A-series data”, whilelight-reception data obtained from the photoelectric converter 116 willbe referred to as “B-series data”. In the following, the principle ofthe phase difference AF will be described with reference to FIGS. 8 to12 showing the A-series data and B-series data obtained from pluraldivided G pixels 11 gr arranged on one Gr line L1 (FIG. 5).

FIG. 8 is a diagram showing a simulation result when the focal plane isdefocused to the 200-μm-closer side from the imaging plane of theimaging element 101. FIG. 9 is a diagram showing a simulation resultwhen the focal plane is defocused to the 100-μm-closer side from theimaging plane. FIG. 10 is a diagram showing a simulation result of thefocused state in which the focal plane corresponds with the imagingplane. FIG. 11 is a diagram showing a simulation result when the focalplane is defocused to the 100-μm-remoter side from the imaging plane.FIG. 12 is a diagram showing a simulation result when the focal plane isdefocused to the 200-μm-remoter side from the imaging plane. In FIGS. 8to 12, the abscissa indicates the positions of the divided G pixels 11gr with respect to the direction of the Gr line L1, while the ordinateindicates outputs from the photoelectric converters 113 and 116. Inaddition, in FIGS. 8 to 12, graphs Ga1 to Ga5 (represented by fulllines) indicate the A-series data, while graphs Gb1 to Gb5 (representedby dashed lines) indicate the B-series data.

Comparison between the respective A-series image sequences and therespective B-series image sequences, which are indicated by the A-seriesgraphs Ga1 to Ga5 and the B-series graphs Gb1 to Gb5 in FIGS. 8 to 12,makes it apparent that a larger defocus amount results in a largeramount of the shift (error) along the direction of the Gr line L1between the A-series image sequence and the B-series image sequence.

When the relationship between the defocus amount and the amount of theshift between a pair of image sequences (A-series and B-series imagesequences) is translated into a graph, the graph Gc shown in FIG. 13 isobtained. In FIG. 13, the abscissa indicates the defocus amount (mm),while the ordinate indicates the difference in the centroid position(expressed by the number of pixels) between the A-series image sequenceand the B-series image sequence. The centroid position X_(g) of an imagesequence can be obtained in accordance with e.g. Equation (1).

$\begin{matrix}{X_{g} = \frac{{X_{1}Y_{1}} + {X_{2}Y_{2}} + \ldots + {X_{n}Y_{n}}}{Y_{1} + Y_{2} + \ldots + Y_{n}}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

In Equation (1), X₁ to X_(n) denote the pixel positions on the Gr lineL1 from the left end for example, and Y₁ to Y_(n) denote the outputvalues of the pixels at the positions X₁ to X_(n), respectively.

As shown by the graph Gc in FIG. 13, the relationship between thedefocus amount and the difference in the centroid position between apair of image sequences is a proportional relationship. When thisrelationship is expressed as an equation in which the defocus amount isDF (μm) and the centroid position difference is C (μm), Equation (2) isobtained.DF=k×C  Equation (2)

The coefficient k in Equation (2) denotes the slope Gk (represented bythe dashed line) of the graph Gc in FIG. 13, and can be acquired inadvance through a factory test or the like.

As described above, the difference in the centroid position (phasedifference) regarding the A-series data and B-series data obtained fromthe divided G pixels 11 gr is obtained in the phase difference AFarithmetic circuit 76. Subsequently, the defocus amount is calculated byusing Equation (2), and the drive amount equivalent to the calculateddefocus amount is given to the focus lens 211. This allows auto focus(AF) control in which the focus lens 211 is rapidly moved to thedetected focal position. The relationship between the defocus amount andthe drive amount of the focus lens 211 is uniquely determined dependingon the design values of the imaging lens 2 mounted on the camera body10.

That is, in the imaging device 1, a pair of image sequences are createdbased on the respective charge signals from the photoelectric converters113 and 116 of the divided pixels 11 gr, which receive the subject lightbeams Ta and Tb that have passed through a pair of partial areas of theexit pupil Ep shown in FIG. 7. Furthermore, the amount of the error(shift) along the direction of the Gr line L1 regarding this pair ofimage sequences is detected to thereby carry out the phase differenceAF.

In view of the depth of field of a typical digital camera, it ispreferable to carry out final focusing through focal detection by acontrast detection system (contrast AF), of which focusing accuracy ishigher than that of the phase difference AF. Therefore, the imagingdevice 1 of the present embodiment also employs the contrast AF forhighly accurate focusing. The principle of this contrast AF will bedescribed below.

In the contrast AF in the imaging device 1, a pixel group of thenon-divided G pixels 11 gb is read out in the AF area defined in a part(e.g., the center part) of the imaging range, and an AF evaluation valueis calculated. This AF evaluation value is calculated as e.g. the totalsum of the absolute values of the differences between adjacentnon-divided G pixels 11 gb in the AF area.

If the AF evaluation values are sequentially calculated in linkage withthe movement of the focus lens 211 in a constant direction, therelationship like that shown in FIG. 14 is obtained between therespective positions of the focus lens 211 and the AF evaluation values.Specifically, in this relationship, in linkage with the focus lensposition change, the AF evaluation value monotonically increases andthen monotonically decreases after reaching a peak Qk. The movement ofthe focus lens 211 is continued until the focal zone is found, i.e., theAF evaluation value passes through the peak Qk.

If AF evaluation values D_(n−1), D_(n), and D_(n+1) near the peak Qk andthe corresponding points P_(n−1), P_(n), and P_(n+1) of the focus lens211 are acquired as shown in FIG. 14, the focus position P_(f) of thefocus lens 211 can be calculated by using quadratic interpolationapproximation expressed by Equation (3).

$\begin{matrix}{{Pf} = \frac{\begin{matrix}{{D_{n - 1}\left( {P_{n + 1}^{2} - P_{n}^{2}} \right)} +} \\{{D_{n}\left( {P_{n - 1}^{2} - P_{n + 1}^{2}} \right)} + {D_{n + 1}\left( {P_{n}^{2} - P_{n - 1}^{2}} \right)}}\end{matrix}}{\begin{matrix}{2\left\{ {{D_{n - 1}\left( {P_{n + 1} - P_{n}} \right)} +} \right.} \\\left. {{D_{n}\left( {P_{n - 1} - P_{n + 1}} \right)} + {D_{n + 1}\left( {P_{n} - P_{n - 1}} \right)}} \right\}\end{matrix}}} & {{Equation}\mspace{14mu}(3)}\end{matrix}$

In the contrast AF, AF evaluation values are obtained in the contrast AFarithmetic circuit 77, and the focus lens 211 is moved by the focusdrive controller 71A to the focus position obtained in accordance withEquation (3). This allows auto focus control with high focusingaccuracy.

The imaging device 1 of the present embodiment performs hybrid AF as thecombination of the above-described phase difference AF employing thedivided G pixels 11 gr and the contrast AF employing the non-divided Gpixels 11 gb. The specific operation of the imaging device 1 regardingthis hybrid AF will be described below.

The above description has dealt with mountain-climbing AF based on ageneral contrast system. However, the present embodiment allows movementto the focus position through the hybrid AF to be described below evenwhen the AF evaluation value does not pass through the peak Qk.

<Operation of Imaging Device 1>

FIG. 15 is a flowchart showing the basic operation of the imaging device1. This operation is executed by the main controller 62.

Initially, the power supply to the imaging device 1 is turned on throughthe main switch 317, so that the imaging element 101 is activated (stepST1).

In a step ST2, the imaging element 101 is set to the live-view readmode. Specifically, as described above, the frame rate is set to 60 fps.Furthermore, an image relating to live-view displaying is created basedon outputs from the non-divided pixels (the non-divided G pixels 11 gb,the R pixels 11 r, and the B pixels 11 b) of the imaging element 101,and the created image is displayed on the EVF 316. In the creation ofthe image, decimation on a horizontal line basis is carried out in sucha way that the data of G pixels on the Gr lines L1 (divided G pixels 11gr), which are absent because being not employed for the image, areinterpolated by the data of the non-divided G pixels 11 gb on the Gblines L2, adjacent to the divided G pixels 11 gr in the obliquedirection.

The reason for the creation of a live-view image by use of thenon-divided pixels (the non-divided G pixels 11 gb, the R pixels 11 r,and the B pixels 11 b) is as follows. Specifically, when an image iscreated by using the divided G pixels 11 gr, it is difficult to stablycreate proper images, because the gains of outputs from thephotoelectric converters 113 and 116 (see FIG. 7) of the divided Gpixels 11 gr are adjusted to proper levels by the AGC circuit in thesignal processor 52, and hence there is a possibility that simpleaddition of these adjusted outputs leads to overflow. Although imageswith proper levels can be created through averaging of outputs from thephotoelectric converters 113 and 116 of the divided G pixels 11 gr,circuits and so on are required for the averaging, which causescomplication of the device configuration.

Therefore, in the imaging device 1 of the present embodiment, alive-view image is created in such a way that output signals from thedivided pixels are excluded and only output signals from the non-dividedpixels are used, in order to stably create proper images withoutcomplication of the device configuration.

In a step ST3, auto exposure control (AE) and auto white balance control(AWB) are implemented. Also in this step, similarly to theabove-described processing of creating a live-view image, the AEprocessing and the AWB processing are executed in such a way that outputsignals from the divided G pixels 11 gr are not employed but only outputsignals from the non-divided pixels (the non-divided G pixels 11 gb, theR pixels 11 r, and the B pixels 11 b), of which inside is not divided,are used.

In a step ST4, it is determined whether or not the shutter button 307 ishalfway pushed (S1) by a user. If the shutter button 307 is halfwaypushed, the operation sequence proceeds to a step ST5. If it is nothalfway pushed, the operation sequence returns to the step ST2.

In the step ST5, the imaging element 101 is set to the AF read mode.Specifically, control of the hybrid AF is started with the frame rateset to 240 fps as described above. Also in the AF read mode, live-viewdisplaying is performed based on output signals from the non-dividedpixels (the non-divided G pixels 11 gb, the R pixels 11 r, and the Bpixels 11 b), which are read out at 60 fps.

In a step ST6, based on outputs from the non-divided G pixels 11 gb inthe AF area in the imaging element 101, an AF evaluation value iscalculated and acquired by the contrast AF arithmetic circuit 77. Thatis, based on an image signal produced in the imaging element 101, an AFevaluation value (focal detection information) to be used for focaldetection by a contrast detection system is acquired.

In a step ST7, the position of the focus lens 211 is detected based onthe number of pulses output from the lens position detector 25 in theimaging lens 2. It is preferable to detect the position of the focuslens 211 at the intermediate time of the period of exposure of thenon-divided pixels used for the calculation of the above-described AFevaluation value.

In a step ST8, phase difference AF is carried out by using outputsignals from the divided G pixels 11 gr in the imaging element 101.Specifically, the centroid position difference regarding A-series dataand B-series data obtained from the photoelectric converters 113 and 116of the divided G pixels 11 gr is obtained in the phase difference AFarithmetic circuit 76, and the focus lens 211 is so driven by usingEquation (2) that this centroid position difference will be eliminated.More specifically, the focus lens 211 is driven to the position detectedthrough the phase difference AF (focal detection position).

In a step ST9, it is determined whether or not the focal adjustmentthrough the phase difference AF has been completed. If the focaladjustment through the phase difference AF has been completed, theoperation sequence proceeds to a step ST10. If it has not been completedyet, the operation sequence returns to the step ST6.

The steps ST6 to ST9 are repeated until the completion of the focaladjustment through the phase difference AF. Due to this repetition, inassociation with the driving of the focus lens 211 by the phasedifference AF, the AF evaluation values (focal detection information)corresponding to the respective positions of the focus lens 211 areacquired as history information of the focal detection. This historyinformation of the AF evaluation value is stored in e.g. a memory in themain controller 62.

In the step ST10, of the history information of the AF evaluation valuescalculated during the phase difference AF, the final AF evaluation valueD_(m) calculated last and the AF evaluation value D_(m−1) that isprevious to the final AF evaluation value D_(m) (previous-to-final AFevaluation value D_(m−1)) are acquired.

In a step ST11, it is determined whether or not the ratio of the finalAF evaluation value D_(m) to the previous-to-final AF evaluation valueD_(m−1) is in the range of 0.99 to 1.01 inclusive. The purpose of thisdetermination is to regard the position of the focus lens 211 as thefocus position to thereby specify the focus position when the ratio ofthe final AF evaluation value D_(m) to the previous-to-final AFevaluation value D_(m−1) is in the range of 100%±1%, because when theratio is in this range, the focus lens 211 has been driven to a positioncorresponding to an AF evaluation value in a range near the peak Qk(FIG. 14), where the slope of the AF evaluation value curve is gentle.

If it is determined in this step ST11 that the relationship0.99≤D_(m)/D_(m−1)≤1.01 is satisfied, i.e., if the focus position of thefocus lens 211 is specified based on the above-described historyinformation of the AF evaluation values (the previous-to-final AFevaluation value D_(m−1) and the final AF evaluation value D_(m)), theoperation sequence proceeds to a step ST19. In contrast, if not so, theoperation sequence proceeds to a step ST12.

In the step ST12, it is determined whether or not the ratio of the finalAF evaluation value D_(m) to the previous-to-final AF evaluation valueD_(m−1) is larger than one. If the relationship D_(m)/D_(m−1)>1 issatisfied, the operation sequence proceeds to a step ST13 based on adetermination that the AF evaluation value is in a monotonic increasestate. If the relationship D_(m)/D_(m−1)≤1 is satisfied, the operationsequence proceeds to the step ST19 based on a determination that the AFevaluation value is in a monotonic decrease state.

In the step ST13, similarly to the step ST6, an AF evaluation value D1is acquired based on outputs from the non-divided G pixels 11 gb in theAF area in the imaging element 101. At the timing immediately after thecompletion of the focal adjustment by the phase difference AF, theabove-described final AF evaluation value D_(m) is acquired as the AFevaluation value D1 from the history information of the AF evaluationvalue.

In a step ST14, additional driving of the focus lens 211 is carried outby 1Fδ equivalent to the focal depth (depth of field) in the samedirection as the drive direction of the phase difference AF. Of the 1Fδ,F denotes the F number indicating the actual diaphragm regarding theimaging lens (imaging optical system) 2, and δ denotes the length twicethe pixel pitch of the imaging element 101 (for example, when the pixelpitch is 6 μm, δ=12 μm).

In a step ST15, similarly to the step ST6, an AF evaluation value D2 isacquired based on outputs from the non-divided G pixels 11 gb in the AFarea in the imaging element 101.

In a step ST16, it is determined whether or not the ratio of the AFevaluation value D2 acquired in the step ST15 to the AF evaluation valueD1 acquired in the step ST13 is in the range of 0.99 to 1.01 inclusive.The purpose of this determination is as follows. Specifically, when theAF evaluation value D2 is obtained through additional driving of thefocus lens 211 by a drive amount W as shown in FIG. 16 for example inthe state in which the AF evaluation value has not reached the peak Qk(FIG. 14) but is monotonically increasing, if the ratio of the AFevaluation value D1 to the AF evaluation value D2 is in the range of100%±1%, i.e., if the difference Ef between the AF evaluation values D2and D1 is smaller than or equal to 1% of the AF evaluation value D1, thefocus lens 211 has been driven to a position corresponding to an AFevaluation value in a gentle slope area near the peak Qk (FIG. 14).Therefore, through the determination in the step ST16, the position ofthe additionally-driven focus lens 211 is regarded as the focus positionto thereby specify the focus position when the AF evaluation value ratiois in the range of 100%±1%.

If it is determined in the step ST16 that the relationship0.99≤D2/D1≤1.01 is satisfied, the operation sequence proceeds to thestep ST19. In contrast, if not so, the operation sequence proceeds to astep ST17 based on a determination that the focus lens 211 has notreached a position corresponding to an AF evaluation value near the peakQk (FIG. 14).

Through the operation of the steps ST13 to ST16, the followingprocessing is executed. Specifically, if the focus position of the focuslens 211 is not specified based on the history information of the AFevaluation values acquired so far, additional driving of the focus lens211 by a drive amount based on the focal depth relating to the imaginglens 2 is carried out and an AF evaluation value is additionallyacquired. Subsequently, the focus position of the focus lens 211 isspecified based on the focal detection history information to which thisadditionally-acquired AF evaluation value (focal detection information)is added.

In the step ST17, it is determined whether or not the additional drivingof the focus lens 211 in the step ST13 has been carried out n (e.g.,n=3) times. The purpose of this determination is to stop the AFoperation based on a determination that the focusing is difficult whenthe additional driving of the focus lens 211 is carried out severaltimes. If the additional driving has been carried out n times, theoperation sequence proceeds to the step ST19. If the number of times ofadditional driving is smaller than n, the operation sequence returns tothe step ST13.

In the step ST18, the focus lens 211 is back-driven to the positioncorresponding to the peak of the AF evaluation value. Specifically, ifit is determined in the step ST12 that the ratio of the final AFevaluation value D_(m) to the previous-to-final AF evaluation valueD_(m−1) is lower than or equal to one, it is determined that the focuslens 211 has passed through the position corresponding to the peak ofthe AF evaluation value, and thus the focus position of the focus lens211 is specified by using Equation (3). Furthermore, the focus lens 211,which has passed through the position (focus position) corresponding tothe peak of the AF evaluation value through the phase difference AF, isback-driven to the specified focus position.

That is, if the focus position of the focus lens 211 is specified basedon the history information of the AF evaluation values acquired duringthe phase difference AF and the specified focus position is differentfrom the focal detection position detected by the phase difference AF,the focus lens 211 is driven to this focus position through theoperation of the step ST18.

In the step ST19, the imaging element 101 is set from the AF read modeto the live-view read mode.

Through the above-described operation of the imaging device 1, focaldetection processing by a phase difference detection system (phasedifference AF) is executed based on charge signals obtained from theplural divided G pixels (second pixels) 11 gr. Furthermore, contrast AFdifferent from the phase difference AF, live-view displaying, AE, andAWB are performed based on charge signals obtained from the pluralnon-divided pixels (first pixels) including the non-divided G pixels 11gb, the R pixels 11 r, and the B pixels 11 b. Therefore, specificprocessing necessary for camera functions other than the phasedifference AF can be executed with high accuracy.

In addition, in the imaging device 1, the divided pixels 11 gr in whichthe plural photoelectric converters 111 to 118 are arranged have thephotoelectric converters 113 and 116 that create the above-describedpair of image sequences (A-series image sequence and B-series imagesequence). Thus, a pair of image sequences used for the phase differenceAF can be created easily.

Furthermore, in the imaging device 1, outputs from the divided pixelsand the non-divided pixels are amplified by different gains in the AGCcircuit of the signal processor 52. Therefore, the output level of thedivided pixels as well as that of the non-divided pixels can be set tothe proper level.

Moreover, in the imaging device 1, the respective non-divided pixels 11gb have a color filter of the same color (green), which allowshighly-accurate and proper phase difference AF.

In addition, in the imaging device 1, the specific processing executedbased on charge signal obtained from the non-divided pixels encompassesprocessing of contrast AF, processing relating to auto exposure control(AE), processing relating to auto white balance control (AWB), andprocessing of creating images relating to live-view displaying (previewdisplaying). Thus, the contrast AF, the AE control, and the AWB controlcan be carried out with high accuracy, and the live-view displaying canbe performed properly.

Modification Examples

-   -   In the above-described embodiment, it is not essential to carry        out phase difference AF by use of an imaging element having        divided pixels (divided G pixels), of which inside is divided.        The phase difference AF may be carried out by using any of        imaging elements 101A and 101B shown in FIGS. 17 and 18.

FIG. 17 is a diagram for explaining the configuration of the imagingelement 101A according to a modification example of the presentinvention.

On Gr lines (see the Gr lines L1 in FIG. 5) of the imaging element 101A,a pair of G pixels 11 g (11 gs, 11 gt) having a green color filter 12 gare arranged to sandwich an R pixel 11 r having a red color filter 12 r.In the G pixel 11 gs, due to a slit SLa of a light-shielding plate 13 a,a light beam Tb that has passed through a left-side part of an exitpupil Ep passes through the green color filter 12 g and forms an imageon a photoelectric converter 110. On the other hand, in the G pixel 11gt, due to a slit SLb of a light-shielding plate 13 b, a light beam Tathat has passed through a right-side part of the exit pupil Ep passesthrough the green color filter 12 g and forms an image on thephotoelectric converter 110.

If the light-reception data obtained from the G pixels 11 gs and 11 gtwith such a configuration are used as the above-described A-series dataand B-series data, phase difference AF can be carried out similarly tothe above-described divided G pixels 11 gr.

Also in such an imaging element 101A, similarly to the imaging element101 of the above-described embodiment, phase difference AF is carriedout by using the G pixels 11 (11 gs, 11 gt) on the Gr lines, whilecontrast AF, live-view displaying, AE, and AWB are carried out by usingR pixels, B pixels, and normal G pixels that are arranged on Gb linesand in which the light-shielding plates 13 a and 13 b are not provided.This allows execution of specific processing necessary for camerafunctions other than the phase difference AF with high accuracy.

FIG. 18 is a diagram for explaining the configuration of the imagingelement 101B according to another modification example.

On Gr lines (see the Gr lines L1 in FIG. 5) of the imaging element 101B,a pair of G pixels 11 g (11 gv, 11 gw) having a green color filter 12 gare arranged to sandwich an R pixel 11 r having a red color filter 12 r.The G pixel 11 gv is provided with a microlens ML of which top surfaceis provided with a light-shielding layer Qa obtained throughblack-coating with a pigment or paint for the entire surface other thana light transmissive area Pa equivalent to the slit SLa in FIG. 17. Dueto this microlens ML, in the G pixel 11 gv, a light beam Tb that haspassed through a left-side part of an exit pupil Ep passes through thegreen color filter 12 g and forms an image on a photoelectric converter110. On the other hand, the G pixel 11 gw is provided with the microlensML of which top surface is provided with a light-shielding layer Qbobtained through black-coating with a pigment or paint for the entiresurface other than a light transmissive area Pb equivalent to the slitSLb in FIG. 17. Due to this microlens ML, in the G pixel 11 gw, a lightbeam Ta that has passed through a right-side part of the exit pupil Eppasses through the green color filter 12 g and forms an image on thephotoelectric converter 110.

If the light-reception data obtained from the G pixels 11 gv and 11 gwwith such a configuration are used as the above-described A-series dataand B-series data, phase difference AF can be carried out similarly tothe above-described divided G pixels 11 gr.

Also in such an imaging element 101B, similarly to the imaging element101 of the above-described embodiment, phase difference AF is carriedout by using the G pixels 11 (11 gv, 11 gw) on the Gr lines, whilecontrast AF, live-view displaying, AE, and AWB are carried out by usingR pixels, B pixels, and normal G pixels that are arranged on Gb linesand in which the light-shielding layers Qa and Qb are not formed on themicrolens ML. This allows execution of specific processing necessary forcamera functions other than the phase difference AF with high accuracy.

In the imaging device of the above-described embodiment, it is notessential that the imaging lens 2 is freely detachable from the camerabody 10. The imaging lens 2 may be fixed to the camera body 10.

In the imaging element of the above-described embodiment, the inside ofthe G pixel does not necessarily need to be divided into eight areas aslong as the pixel inside is divided into two or more areas. Furthermore,it is not essential to divide the G pixels. R pixels or B pixels may bedivided.

For the AF evaluation value of the above-described embodiment, it is notessential to calculate the total sum of the absolute values of thedifferences between adjacent non-divided G pixels 11 gb. It is alsopossible to calculate the total sum of the absolute values of thesquares of the differences between adjacent pixels.

In the operation of the imaging device of the above-describedembodiment, it is not essential to determine in the step ST11 of FIG. 15whether or not the ratio of the final AF evaluation value D_(m) to theprevious-to-final AF evaluation value D_(m−1) is in the range of100%±1%. For example, whether or not the ratio is in the range of100%±3% may be determined.

In the operation of the imaging device of the above-describedembodiment, it is not essential to carry out additional driving of thefocus lens 211 by 1Fδ in the step ST14 of FIG. 15. Additional driving by2Fδ may be carried out. That is, the drive amount is based on the focaldepth relating to the imaging lens 2.

The divided G pixel in the above-described embodiment does notnecessarily need to be divided into plural areas along the direction ofthe Gr lines L1 shown in FIG. 5 (horizontal direction). It may bedivided into plural areas along the vertical direction. In this case,phase difference AF is carried out based on the amount of the shift inthe vertical direction regarding a pair of image sequences (A-seriesimage sequence and B-series image sequence) obtained from the divided Gpixels.

It should be noted that the present invention is not limited to theaforementioned embodiments and may be modified in various ways withinthe spirit of the invention.

What is claimed is:
 1. An imaging device, comprising: an imagerconfigured to: generate an image signal of a subject; and determine anin-focus position of a focus lens based on a contrast focus evaluationvalue and a phase difference focus defocus value, wherein the contrastfocus evaluation value is determined based on a contrast auto focus (AF)method from a first part of the image signal read from a normal pixel ofthe imager, and the phase difference focus defocus value is determinedbased on a phase difference AF method from a second part of the imagesignal read from a phase difference pixel of the imager; and at leastone processor configured to drive the focus lens to the in-focusposition that corresponds to a peak focus evaluation value among aplurality of focus evaluation values, wherein the focus lens is drivenbased on a determination that a ratio of the peak focus evaluation valueto a previous focus evaluation value, prior to the peak focus evaluationvalue, is within a range of values.
 2. The imaging device according toclaim 1, wherein the peak focus evaluation value is highest among theplurality of focus evaluation values.
 3. The imaging device according toclaim 1, wherein the normal pixel comprises a first color filter and thephase difference pixel comprises a second color filter, and the firstcolor filter and the second color filter are of same color.
 4. Theimaging device according to claim 1, wherein the normal pixel and thephase difference pixel are along a same direction.
 5. A method,comprising: in an imaging device: generating, by an imager, an imagesignal of a subject; determining, by the imager, an in-focus position ofa focus lens based on a contrast focus evaluation value and a phasedifference focus defocus value, wherein the contrast focus evaluationvalue is determined based on a contrast auto focus (AF) method from afirst part of the image signal read from a normal pixel of the imager,and the phase difference focus defocus value is determined based on aphase difference AF method from a second part of the image signal readfrom a phase difference pixel of the imager; and driving, by at leastone processor, the focus lens to the in-focus position that correspondsto a peak focus evaluation value among a plurality of focus evaluationvalues, wherein the focus lens is driven based on determination that aratio of the peak focus evaluation value to a previous focus evaluationvalue, prior to the peak focus evaluation value is within a range ofvalues.
 6. The method according to claim 5, wherein the peak focusevaluation value is highest among the plurality of focus evaluationvalues.
 7. The method according to claim 5, wherein the normal pixelcomprises a first color filter and the phase difference pixel comprisesa second color filter, and the first color filter and the second colorfilter are of same color.
 8. The method according to claim 5, whereinthe normal pixel and the phase difference pixel are along a samedirection.
 9. A non-transitory computer-readable medium having storedthereon, computer-executable instructions, which when executed by acomputer, cause the computer to execute operations, the operationscomprising: generating an image signal of a subject; determining anin-focus position of a focus lens based on a contrast focus evaluationvalue and a phase difference focus defocus value, wherein the contrastfocus evaluation value is determined based on a contrast auto focus (AF)method from a first part of the image signal read from a normal pixel ofan imager, and the phase difference focus defocus value is determinedbased on a phase difference AF method from a second part of the imagesignal read from a phase difference pixel of the imager; and driving thefocus lens to the in-focus position that corresponds to a peak focusevaluation value among a plurality of focus evaluation values, whereinthe focus lens is driven based on determination that a ratio of the peakfocus evaluation value to a previous focus evaluation value, prior tothe peak focus evaluation value is within a range of values.
 10. Thenon-transitory computer-readable medium according to claim 9, whereinthe peak focus evaluation value is highest among the plurality of focusevaluation values.
 11. The non-transitory computer-readable mediumaccording to claim 9, wherein the normal pixel comprises a first colorfilter and the phase difference pixel comprises a second color filter,and the first color filter and the second color filter are of samecolor.
 12. The non-transitory computer-readable medium according toclaim 9, wherein the normal pixel and the phase difference pixel arealong a same direction.